The forklift truck has been around for a century, and today it is found in every warehouse operation around the world. Commercial and industrial goods of all kinds are moved in bulk for economic efficiency. Forklift trucks and hand operated jacks, usually referred to as “manual jacks,” typically use forks, that is, at least a pair of horizontally protruding blades or tines as load bearing elements. The forks are mechanized in order to lift loads clear of ground surfaces so that the loads may be moved from place to place. The forks may be engaged with a pallet that has goods stored on top. In this manner the goods may be lifted, moved, and then lowered or raised to a new location. This procedure is very well known in the field of the invention.
“Forklift” is the common generic term used to refer to the various types of materials handling equipment that uses a fork for moving loads. Fork type equipment may be informally classified as follows:
class 1—electric motor rider trucks;
class 2—electric motor narrow aisle trucks;
class 3—electric motor or hydraulic hand operated jacks;
class 4—internal combustion engine trucks—cushion tires;
class 5—internal combustion engine trucks—pneumatic tires;
class 6—electric and internal combustion engine tractors; and
class 7—rough terrain forklift trucks.
All of the foregoing classes of fork type equipment have in common that they are types of forklift jacks, or simply “forklifts” or “materials handling” equipment. Jacking mechanisms typically are motorized or hydraulically operated. A forklift may be a powered industrial truck; that is, a forklift truck, used to lift and move materials horizontally and vertically. A forklift may also be a manual jack; typically a hydraulic lifter which may be operated, propelled, and steered manually. Both the forklift truck and manual jack are designed for handling heavy loads which may or may not be palletized, and for moving such loads over relatively short distances. Of course, there are exceptions and hybrid types of forklifts. Collectively these will be termed “forklifts” or “materials handling equipment” herein throughout.
Typically, the fork element of such materials handling equipment has wheels which may be retracted into its blades so that the blades may be dropped to a floor surface. The wheels may be extended into contact with the floor surface as the blades are lifted. Therefore, the extended wheels are relied upon to help support loads placed on the fork as a load is moved and maneuvered. Because the blades must be able to fit into a pallet with clearance, they must be relatively thin and flat, dimensions that necessitate associated blade wheels have a relatively small diameter in order to fit inside the blades. This has several drawbacks, including the fact that small diameter wheels have difficulty in traversing rough or cracked floor surfaces and doorway thresholds, and having small circumferences such wheels tend to wear out quickly.
Blade wheels support much of the weight of a load during forklift operations. Blade wheels may be axially elongated so as to reduce instantaneous stress on floor surfaces. Typical blade wheels have a limited useful life as they wear, crack, spall, and develop flats so that they must be replaced frequently. Therefore, there is a need for materials handling equipment load and drive wheels that will minimize damage to floor surfaces, have a longer operating life than wheels in current use, and are able to more easily traverse uneven floor surfaces and thresholds. The presently described and illustrated compound sinusoidal wheel has been shown through extensive testing to have significant advantages over forklift and materials handling equipment load and drive wheels in current use.